The invention relates to a new process and a new kit for applying a natural appearing wood grain to a door, window or other item or component made of any suitable material having a wood grain texture. The appearance of the final finish is highly durable, very simple and rapid to apply and results in a finish which can closely simulate the appearance of natural clear coated wood. The invention achieves these long-standing industry objectives without the use of a clear coat of the type that is highly sensitive to failure due to yellowing and delamination, problems that have plagued the industry looking for a successful wood graining process for simulated wood textured surfaces.
Many of the problems with achieving a natural wood appearance in a simulated wood door have been addressed and solved by the art. U.S. Pat. No. 5,075,059 to Green, for example, describes a method which includes a first step of compression molding fiber reinforced polyester door skins with closed areas dense with deep grains, open areas with a generally lesser concentration of deep grains and reduced depth grains adjacent steeply angled trim areas. The open areas have a predetermined roughness, which is provided by the mold half used in compression molding. In the subsequent steps, the molded door skin is sprayed with a mixture of artist's oil cut 1:1 with mineral spirits on a fluid ounce basis. After twenty minutes, the sprayed mixture is rubbed into the external surface, and the door skin is then placed vertically in a forced air oven for about one hour at about 120° F. Drying under ambient conditions takes far longer and is not practical in many situations. Also, the color layer is not bonded to the substrate and will easily peel off with an overcoat material, such as the standard final step urethane top coat, which Green states may be applied to the dried coloring layer. By providing deep grains of varying density over most of the door skin surface, but reduced grain depths adjacent to steeply embossed or bossed trim sections, the external surfaces of the panel door are said to more realistically simulate a wood grain appearance, while the reduced depth of the grains in steeply angled areas minimizes risk of deformation during mold release. Unfortunately, because the achievement of color depends on the first coloring step and a clear overcoat, durability is less than might be desired.
The prior art that relies upon the use of a transparent or pigmented translucent mixture as a first coat requires the user to have a good sense of color selection and matching. This need is exaggerated by the fact that different manufacturers of doors and other trim parts provide their own substrate base colors. Even though two pieces might seem to be the same “white” color, they are often different in the way that they receive the stain. This makes it difficult for a homeowner to properly match colors. Also, distinctly different base colors will cause distinctly different stained colors. Even where the manufacturer tries to match substrate color, it is common to employ trim pieces, such as around a window or sidelight, of different materials from the main structure. The use of a staining pigment layer as the first coat cannot be applied by other than the most skilled workers to match colors between components and even then the finish has inherent limitations due to its makeup.
In U.S. Pat. No. 5,534,352, Pittman, et al., describe a process for pre-finishing wood composite panels and/or structures having flat and contoured surfaces to result in a structure exhibiting the appearance of natural hard wood. The process includes a number of steps designed to facilitate industrial scale, machine production. To that end, they employ a ground coat in a first step, then a non-adherent “dry buffing glaze” which is selectively removed, and finally they apply a sealer to retain the remaining buffing glaze in textured ticks of the substrate. The dry buffing glaze is preferably a waterborne coating, applied to the substrate as a liquid and then flash dried to yield a dull powdery appearance. The true color of the glaze is not evident until it is wetted in a subsequent toning or top-coating step. The glaze has a high proportion (e.g., at least about 80 weight %) of inert pigments so as to make it powdery and easily buffed from flat surfaces of the substrate. This type of powdery buffing composition, unfortunately, has no bonding capability to the base and tends to provide a plane of weakness where the ultimate glazed finish can easily separate. When separated, the finish is irreparably discolored in the area of the separation. The use of a clear glaze is necessary for protection of the color, but is highly susceptible to ultraviolet light damage. Clear finishes of this type rapidly yellow and lose their initial physical strength.
The Pittman, et al., patent makes it clear that the product is not complete following the pre-finishing process, but is further prepared and finished or semi-finished. The process is not simple, such as would be suitable for a home decorating project. They make this clear indicating that the process requires machine operation. They emphasize that, if the substrate were hand-rubbed during this step, the pressure of a glazing cloth could wipe the glaze out of the wood grain ticks—yielding a less realistic appearance. Following the buffing operation, a sealer is applied to bind the dry buffing glaze to the substrate and protect the panel finish during storage, shipping, and handling of the pre-finished substrate. The clear sealer, preferably a clear acrylic sealer, is sprayed on the substrate. The clear sealer also renders the substrate receptive to lacquer or solvent-based glazes and toners that may be applied to the substrate as a final finishing step. The basic process is difficult to perform and results in a coating that has limited adherence to the substrate, has limited durability and cannot be easily repaired.
One commercial form of wood graining kit, available from Pease Industries, Inc., of Fairfield, Ohio, is a solvent-based system comprising a wood stain and a clear topcoat. The literature on using the kit states that the stain is applied on a door using a lint-free cloth in a circular motion, working the stain into the embossed grain pattern. Next, a stain cloth is used to smooth the stain in the direction of the grain. The directions specifically say that excess stain should not be wiped off. Working the same area with a clean soft bristle brush to gently feather-out any streaks or lap marks follows this. If the stain color is not satisfactory, the stain can be cleaned off with mineral spirits before it dries, and applied again. If the first coat is too light, the literature suggests waiting 48 hours before a second coat is applied in the manner of the first coat. To complete the job, a polyurethane topcoat is then applied. The stain must be thoroughly dry before top-coating—48 to 72 hours drying time is recommended.
Another type of commercial graining kit has been available with an opaque stain as one coat and a dark graining coat. The opaque coat would uniformly cover the surface being worked on and allowed to dry. Then, the dark graining coat would be applied with a brush or the like to paint on a grain pattern. Thus, the graining depended upon the artistic ability of the person doing the work.
In an attempt to directly coat synthetic molded doors, which are generally nonporous, U.S. Pat. No. 6,358,614 to Porter describes a weatherable coating based on a stain/topcoat system. The coating comprises a pigmented stain having substantially a single binder resin, which promotes adherence of a topcoat and a topcoat that is an aqueous dispersion of a film forming polymer and a curable organopolysiloxane microemulsion. The topcoat is said to display exceptional adhesion and weatherability to surfaces stained with the specially formulated pigmented stain. U.S. Pat. No. 6,120,852 and U.S. Pat. No. 5,948,849 are directly related.
The Porter coating is applied in two steps: a specially formulated pigmented stain coating and a compatible transparent topcoat. The stain is a solvent-based composition containing from 20 to 40% of a volatile solvent such as slowly evaporating solvents and solvents that exhibit fast to moderate evaporation, such as mineral spirits, naphtha, petroleum distillate, and the like. The topcoat is aqueous and includes from 25 to 55% of a water-dispersible non-polysiloxane film-forming polymer, 2 to 25% of a curable organopolysiloxane in the form of an emulsion and water superficial to the pigmented stain coating. The use of the curable organopolysiloxane emulsion is said to be necessary to make the topcoat compatible with the specially formulated stain. The use of solvents is, of course, less than desired, and the stain coat can provide a less than complete color treatment that must be preserved with a topcoat.
The Porter stain is applied directly to a non-porous thermoset and/or thermoplastic composite by conventional means, i.e., by brushing, spraying, sponging, rolling, wiping, and the like. The stain is specially formulated for these nonporous surfaces and excess stain is removed by wiping with a clean lint free rag, a china bristle brush or the like. The stain is generally allowed to dry for approximately 48 hours at room temperature under dry conditions. After the stain is dry, the topcoat is applied, preferably as two layers, with a total dry thickness of 10-100 μm. The topcoat is preferably applied as two layers and dried for three hours between coats.
There remains a need for a process and a kit useful for imparting a durable, realistic wood-grained appearance to a wood-grain-textured substrate. There is particular need for a simple process and means for imparting a realistic, durable wood-grain appearance to molded doors, windows and other wood-simulating panels, composites or components, which have one or more surfaces textured to simulate the regular grain patterns of ticks associated with any of a variety of types of wood.